Results 6-Alkenyl p-keto esters of type la are accessible, in principle, via alkylation of the dianion of a keto ester12 with an allylic halide. Although Casey and Marten reported that alkylation of the dianion of methyl acetoacetate with l-bromo-3-methylbut-2-ene (7) affords 8, 13 it was found more convenient to prepare this substrate by carbomethoxylation of the anion of 6-methylhept-5-en-2-one (9) with dimethyl carbonate. This route, which led to 8 in ...
